Method of protecting tin-packaging against corrosion and making them glossy

ABSTRACT

Tin-packings, i.e. tin-cans for food are protected against corrosion and made glossy at the same time by a method in which a tin-packing is treated with a mixture of inorganic and organic corrosion inhibitors having a common anion and having a synergistic effect together with washing and brightening agents.

United States Patent 21/57, 2; 134/2, 25 R, 25 A; 252/389 R, 389 AJuchniewicz July 22, 197 5 METHOD OF PROTECTING [56] References CitedTIN-PACKAGING AGAINST CORROSION UNITED STATES PATENTS AND MAKING THEMGLOSSY 2.643.177 6/1953 Wachter et a1 21/27 R ux [75] Inventor; RomualdJuchniewicz, Gdansk, 2.675.351 4/1954 U1mer et a1. 2.1/2.7 R Poland2.815.328 12/1957 Grcen ct a1. 252/389 R x 2.817.636 12/1957 Barker252/389 R X 1 3] Assign t hnika Gdanska. Gdansk, 2.901.438 8/1959 Rogers252/389 A x Poland 2.943.909 7/1960 Wachter et a1. 21/2.7 R 3.046.2307/1962 Berger 252/389 R X [221 111 1973 3.234.144 2/1966 Morehousc252/389 R [211 App! NO: 405 59 3,240.707 3/1966 Du1at 252/389 R X3,445.179 5/1969 Jansen 21/27 R Related US. Application Data 3,510,4365/1970 Silverstein et al 2l/2.7 R X [60] Division of Ser. No. 267,983,June 30, 1972, Pat. No.

3,822,998, which is a continuation of Ser. No. Primary E,mminer Barry S.Richman 7 1969, abandoned- Attorney, Agent. or FirmWaters, Schwartz &Nissen \[30] Foreign Application Priority Data ABSTRACT Oct. 10, 1968Poland 129973 Tin-packings, 1.6. tin-cans for food are protected 52 us.01 21/2.7 R; 21/2; 21/27 A; against Corrosion and made glossy at thesame time y 57; 154 2; 34 25 252 3 9 R a method in which a tin-packingis treated with a mix- 5 hm C231? 11/12; C23]: 1 ture of inorganic andorganic corrosion inhibitors hav- 3 11/18 ing a common anion and havinga synergistic effect 158 Field of Search 21/2.7 R, 2.7 A, 2.5 A, mgeherwith Washing and brightening agents- 2 Claims, N0 Drawings METHOD OFPROTECTING TIN-PACKAGING AGAINST CORROSION AND MAKING THEM GLOSSYCROSS-REFERENCE TO RELATED APPLICATIONS:

This application is a division of Ser. No. 267,983 filed June 30, 1972and now US. Pat. No. 3,822,998, which in turn is a continuation of Ser.No. 872,748 filed Oct. 30, 1969 and now abandoned.

BACKGROUND OF THE INVENTION:

1. Field of the Invention:

The invention relates to protecting tin packings against corrosion andrendering them glossy.

2. Prior Art:

The known method of protecting tin packings against corrosion consistsmainly in coating the packings, after sterilization or pasteurizationthereof, with temporary protective agents in the form of an emulsion, agrease layer or a paraffin layer.

A disadvantage of these methods is the fact that they provideinsufficient protection against corrosion since, in spite of thepresence of the layer of inhibiting agent, the corrosion process whichis initiated during sterilization or pasteurization continues while thetin-packing is stored.

In the literature Applicant has found no method for protecting againstcorrosion and imparting a gloss to tin-plate packings which involve theintroduction of a mixture of inhibitors into the water used during thesterilization and pasteurization processes. On the other hand, there area number of patents disclosing the use of inorganic and organicinhibitor mixtures with various additives causing a synergistic effectfor many industrial applications. These mixtures, mainly empiricallyarrived at, are not based on the theoretical considerations involved inthe present invention.

DETAILED DESCRIPTION OF THE INVENTION:

The object of the present invention is the provision of a method ofprotecting tin-packings, particularly for tinned foods, againstcorrosion and for making them glossy.

The method according to the present invention is based on the fact thata mixture of inorganic and organic corrosion inhibitors having a commonanion produces a synergistic effect in preventing corrosion and with thecooperation of washing and brightening agents, the mixture causes astrong anodic polarization in the steel tin coating cell. The mixture ofinhibitors forms a stable complex which, by being absorbed on thesurface of the metal, decreases the binding force of the metal with thepassivating oxygen, maintains the potential of the packing below thecritical value at which pit formation occurs and deepens the passivatingproperties of the solution. The processes occuring in the cell cause ananodic dissolution of steel and its immediate passivation. Under suchconditions, the surface of the packing undergoes electropolishing andglossing. The electrochemical process of precipitation in the pores ofthe coating and the process of coagulation of some colloids proceedsimultaneously, thus sealing the tin coating on the steel.

The purpose of the present invention is to protect tinplate packingsagainst corrosion and to make them glossy during the sterilization orpasteurization process.

This purpose has been achieved by using a mixture of chemical compoundsof a strictly determined qualitative and quantitative composition inwhich the process of protecting against corrosion and that of impartinga gloss to the packing proceed jointly with the sterilization orpasteurization process.

According to the chemical composition of the water and its hardness, aswell as to the kind of sheet metal used for the packings, an inhibitormixture, consisting of an inorganic inhibitor, an organic inhibitorhaving a common anion, a washing agent and a brightener, is dissolved inwater and added with continuous stirring. to the water contained in thepasteurization tank or autoclave which is filled with packings forsterilization. In steam autoclaves, the mixture is placed in the form ofa paste in a perforated container in the autoclave at the steam inlet.In horizontal autoclaves the bottom of the autoclave is strewn with themixture or the mixture may be placed in a perforated container near thesteam or water inlet.

Among the inorganic inhibitors there are included. disodium phosphate,sodium hexametaphosphate, water glass, sodium nitrite, and borax. Amongthe organic inhibitors having a common anion and which together with theother additives produces a synergistic effect, there are, for example,the phosphates: triethanolamine phosphate, hexamethylenetetraminephosphate, p-nonylphenol phosphate, styrophene phosphite; the silicates:4-phenoxysilane, 4-butoxysilane, calcium silanolate,aminoalkylpolysiloxane; the nitrites: guanidine nitrite, diisobutylaminenitrite, piperidine nitrite, dicyclohexylamine nitrite; the borates:hydrated cyclohexylamine borate, triethanolamine borate, boric acidtriphenyl ester. As the washing agents, there are used water glass,sodium dodecylbenzenesulphonate, ethoxylized anhydrosorbite oleate,ethoxylized pentaerythrite monooleate, ethoxylized pnonylphenol; and asthe brightener there is used sodium perborate.

The amount of the inhibitor mixture is determined in relation to theamount of water used for pasteurization or sterilization of thetin-packings. It is also dependent on the chemical composition andhardness of the water, as well as on the kind of sheet metal used.'Theamount is usually 0.05-O.6% by weight; the percent share of theindividual components of the mixture is as follows:

inorganic inhibitors 40 60% organic inhibitors having a common anion l545% washing agents 10 20% brightener 5 20% The solutions based onphosphate inhibitors have a pH of about 9, nitrite solutions always areabove pH 6.5, silicate solutions are up to pH 7, and borate solutionsabout pH 7. The modulus of the water glass should be about 2 4.

After the pasteurization or sterilization process, the dried or wipedpacking is passed, without any necessity of using an additionalpreservative, to storage, where the packings are isolated from oneanother by means of plates which are saturated with a mixture ofinhibitors of which one may be a volatile corrosion inhibitor.

The method according to the present invention is more fully explained inthe following Examples.

EXAMPLE I To I000 liters of technological water of of German hardness,which are used for the sterilization of 1000 0.5 kg cans made ofelectrolytic tin-plate. there are added with constant stirring, asolution consisting of the following previously dissolved in water:

250 g of disodium phosphate 100 g of triethanolamine phosphate 100 g ofsodium dodecylbenzencsulfonate I00 g of sodium perborate 250 g of waterglass.

The above is a homogeneous inhibitor solution having a pH value of about9, and the sterilization is carried out therein. The cans, after beingdried or wiped free of the superficial water layer, are directed,without any additional preservation, to storage where they are separatedfrom one another by means of plates saturated on both sides with sorbatemonooleate. The thus secured packings do not corrode at all during a twoyear period of storage.

EXAMPLE II To 500 liters of technological water of 2 of German hardnessused for the pasteurization of 500 l kg packings made of hot tin-plate.the following is added with continuous stirring, after being previouslydissolved in water;

200 g of sodium nitrite 90 g of diisohutylamine nitrite 75 g ofethoxylized pentaerythrite monoleate 75 g of sodium perborate 250 g ofwater glass.

The above is a homogeneous inhibitor solution having a pH value of about8.5 and pasteurization is carried out therein. The dried packings areseparated from each other by means of plates saturated on both sideswith ethoxylized pentaerythrite monooleate. Thus secured packings do notcorrode within up to two years of storage.

EXAMPLE lll ln a steam pressure autoclave, at the steam inlet, there issuspended a perforated container containing an inhibitor mixture ofpaste consistency and composed of:

250 g of water glass 250 g of sorbate monooleate 150 g of sodiumperborate 250 g of disodium phosphate 50 g of hexamethylenetetraminephosphate.

The steam jet breaking against the container becomes saturated with theinhibitors. After the sterilization process the dried cans are directed,without any additional preservation, to storage where the cans areseparated from each other by means of plates saturated on both sideswith a 1:1 mixture in paraffin oil of sorbate monooleate andpentaerythrite oleate. Thus secured packings do not corrode even aftertwo years.

EXAMPLE IV To 500 liters of technological water of of German hardness,used for the pasteurization of 500 1 kg packings made of electrolytictin-plate there are added with continuous stirring, previously dissolvedin water:

250 ml of water glass of a modulus of 2-4 100 g of 4-butoxysilane g ofethoxylized anhydrosorbite oleate 70 g of sodium perborate.

The above is a homogeneous inhibitor solution having a pH value of about7 and the pasteurization is carried out therein. The cans, after beingdried or wiped free of superficial water are directed, without anyadditional preservation, to a storage area where they are separated fromeach other by means of plates saturated on both sides with a mixture ofsorbate monooleate and pentaerythrite monooleate with an addition ofdicyclohexylamine nitrite. These packings do not corrode even after 2years of storage.

EXAMPLE V To 500 liters of technological water of 14 of German hardness,used for the sterilization of 500 0.5 kg packings made of hot tin-plate,there is added with continuous stirring to an autoclave, a watersolution of:

200 g of borax 100 g of triethanolamine borate g of ethoxylizedpentaerythrite monooleate 75 g of sodium perborate.

The above is a homogeneous inhibitor solution having a pH value of about7.5 and sterilization in a pressure autoclave is carried out using saidsolution. The cans, after being dried or wiped free of the superficialwater layer are directed, without any additional preservation, tostorage, where they are separated from each other by means of platessaturated on both sides with paraffin oil, to which 50% ofpentaerythrite monooleate has been added. The thus treated packings donot corrode, even after two years of storing.

EXAMPLE Vl in a horizontal autoclave, the bottom of the auto clave isstrewn with a mixture consisting of the following inhibitors:

300 g of water glass 250 g of disodium phosphate g of p-nonylphenolphosphate 75 g of ethoxylized pentaerythrite monooleate 100 g of sodiumperborate Then there are placed into the autoclave 3 baskets filled with2000 0.25 kg packings. The packings are covered with about 1000 litersof water and sterilization is carried out according to the conventionaltechnological requirements.

After the sterilization process the cans, dried or wiped free of thesuperficial water, are directed to storage. If two autoclaves areoperating in parallel, the inhibitors are to be introduced during threesterilization operations and the fourth operation is carried out withoutinhibitors.

The invention finds application in various fields of the food industryproducing tinned preserves. The serviceable and technical advantagesresulting from the use of the present invention consist in theelimination of corrosion of packings during the production and storage,improvement of the external appearance, preventing corrosion of theautoclaves, vehicles and equipment used in the sterilization orpasteurization process. Furthermore, the packings need no grease oremulsion coating, thus creating better labeling conditions and improvingthe external appearance of the packings, since the labels have no fatdrippings. Also. the costs of cleaning the packings are decreased.

What is claimed is:

l. A method for preventing corrosion and imparting glossiness totin-packings during the sterilization or pasteurization thereof withwater, said method comprising adding to the water used in saidsterilization or pasteurization, a mixture comprising (a) water glass;(b) an organic derivative having an anion in common with water glass;(c) a washing agent and (d) a brightening agent, the organic derivativebeing at least one organic silicate selected from the group consistingof 4-phenoxysilane, 4-butoxysilane, calcium silane, andamino-a1kylpolysiloxanes.

2. A method for preventing corrosion and imparting glossiness totin-packings during the sterilization or pasteurization thereof withwater, said method comprising adding to the water used in saidsterilization or pasteurization, a mixture comprising (a) sodiumnitrite; (b) an organic derivative having an anion in common with sodiumnitrite; (c) a washing agent and (d) a brightening agent, the organicderivative being at least one organic nitrite selected from the groupconsisting of dicyclohexylamine nitrite. diisobutylaminc nitritepiperidine nitrite and guanidine nitrite.

1. A METHOD FOR PREVENTING CORROSION AND IMPARTING GLOSSINESS TOTIN-PACHINGS DURING THE STERILIZATION OR PASTEURIZATION THEREOF WITHWATER SAID METHOD COMPRISING ADDING TO THE WATER USED IN SAIDSTERILIZATION OR PASTEURIZATION, A MIXTURE COMPRISING (A) WATER GLASS,(B) AN ORGANIC DERIVATIVE HAVING AN ANION IN COMMON WITH WATER GLASS (C)A WASHING AGENT AND (D) A BRIGHTENING AGENT THE ORGANIC DERIVATIVE BEINGAT LEAST ONE ORGANIC SILICATE SELECTED FROM THE GROUP CONSISTING OF4PHENOXYSILANE 4-BUTOXYSILANE CALCIUM SILANE ANDAMINOALKYLPOLYSILOXANES.
 2. A METHOD FOR PREVENTING CORROSION ANDIMPARTING GLOSSINESS TO TIN-PACKINGS DURING THE STERILZATION ORPASTEURIZATION THEREOF WITH WATER SAID METHOD COMPRISING ADDING TO THEWATER USED IN SAID STERILZATION OR PASTEURIZATION A MIXTURE COMPRISING(A) SODIUM NITRITE (B) AN ORGANIC DERIVATIVE HAVING AN ANION IN COMMONWITH SODIUM NITRITE, (C) A WASHING AGENT AND (D) A BRIGHTENING AGENT THEORGANIC DERIVATIVE BEING AT LEAST ONE ORGANIC NITRITE SELECTED FROM THEGROUP CONSISTING OF DICYCLOHEXYLAMINE NITRITE DIISOBUTYLAMINE NITRITEPIPERIDINE NITRITE AND GUANIDINE NITRITE.